For a few decades, some vehicle models have been equipped with proximity sensors to help the driver avoid running into obstacles in certain situations, such as when going in reverse. These sensors have generally been of the exposed type, where the vehicle has a small opening in a panel or fascia, and the sensor is mounted in the opening where it extends somewhat from the surface. To make the sensors less visually distracting, they are sometimes colored based on the vehicle surface where they are mounted. Nevertheless, the sensors are usually noticeable, as they are often placed in otherwise smooth decorative surfaces.